Abstract
Purpose :
To describe the structural macular retinal thickness changes that occur in juvenile marmosets as a function of age and compared to those in marmosets that developed myopia.
Methods :
Refractive error (Rx), axial length (AL), and sub and parafoveal retinal thickness (RT, 0.5-3.0mm from foveal pit, 360 deg) were measured in 13 marmosets (N=7 treated with -5D; N=6 age-matched controls) from 10 to 20 weeks of age using the Nidek autorefractor, a high frequency A-scan ultrasound and the Bioptigen Spectral Domain Optical Coherence Tomography (SD-OCT) respectively. Ultrasound and square volume SD-OCT (12x12mm, 100 B-scans, 1000 A-scans/B-scan) were performed under anesthesia (alfaxan, 1.5mg/kg, im). Retinal thickness (RT) was quantified using The Iowa Reference Algorithms v3.6 (Iowa Institute for Biomedical Imaging).
Results :
With age, the eyes of control marmosets emmetropized with a slight overall retinal thickening (change in Rx, AL and average RT, mean±SE:-1.74±1.02D, 0.67±0.03mm, 5.07±6.88μm). The temporal and superior quadrants thickened at a faster rate than the inferior and nasal regions (12.06±5.49, 9.72±5.85, 7.54±5.43 and 2.02±6.70μm respectively, p>0.05). In all quadrants except in the superior, the age-related retinal thickening decreased with eccentricity. Prior to treatment, the retinas of animals that were larger in size were also thinner on the inferior and nasal region closer to the ONH (R=-0.59, p<0.05; R=-0.50, p=0.08 respectively). After treatment, -5D treated eyes grew faster and developed myopia (change in Rx and AL:-5.87±1.24D, 0.95±0.04mm), and also experienced an overall retinal thicknening (change in RT; temporal:16.27±7.40, superior:9.11±7.06, inferior:6.00±4.43, nasal:4.58±7.39μm respectively, p>0.05). In these myopic eyes, the inferior outermost region thickened at a slower rate as eyes grew longer (R=-0.74, p=0.09).
Conclusions :
Retinal thickness can be safely and reliably measured non-invasively in-vivo in marmosets under anesthesia. As it occurs in infant human eyes, the overall subfoveal and parafoveal retina of marmosets thickens with age. Within each quadrant, the para-foveal retina thickening decreased with eccentricity. Marmoset eyes that developed myopia and grew at a faster rate experienced a slight slower age-related thickenining of the inferior retina, possibly suggesting early anatomical differences during myopia development.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.